HIV-1 infection is commonly accompanied by injury to the central nervous system. Affected individuals frequently exhibit serious, progressive behavioral and neurological complications. Although the precise molecular and cellular pathogenetic processes associated with HIV encephalopathy remain unknown, accumulating evidence suggest toxicity tot he CNS amy be mediated indirectly, in part, by host derived factors such as cytokines, produced in response to the viral infection. This proposal focuses on the hypothesis that a key antiviral cytokine IFN-alpha, produced systemically and by infiltrating immune cells or resident brain cells, contributes to CNS injury during HIV-infection. To test this hypothesis, a well defined transgenic approach was employed in which the expression of IFN-alpha was targeted to astrocytes using a glial fibrillary acidic protein-IFNalpha1 fusion gene construct. This approach has provided a unique and powerful model to study the neuropathogenic consequences of the constitutive production of IFN-alpha from astrocytes in the intact CNS. Preliminary pathological characterization of so-called GIFN transgenic mice has unveiled wide-ranging structural and molecular alterations of the CNS thereby directly supporting the view that IFN-alpha, and likely therefore, other members of the IFN family, may have a causal role in the genesis of HIV encephalopathy. Here, we propose to further expand the scope and detail of the neuropathological assessment in an existing as well as in new stable lines of GIFN mice to be developed. This assessment will employ an established battery of tests to examine CNS alterations the molecular and cellular levels., including RNase protection assay, in situ hybridization, northern blot hybridization, protein immunoblot assay, conventional light and laser confocal microscopy of immunolabeled brain sections and electron microscopy. Functional CNS alterations in the GIFN mice will be determined at the behavioral, electrophysiological and neuroendocrine levels and where possible be linked to specific molecular and cellular alterations. The neurological impact of different pathogenetic factors will be assessed in the GIFN mice by: i) cross-breeding of the GFAP-IFN mice with mice from other transgenic backgrounds (e.g. GFAP-IL6 or GFAP-gp120), ii) intra- neural infection with neurotropic viruses and, iii) back-cross breeding with SCID mice to develop immunodeprived GFAP-cytokine transgenic animals. These studies will recapitulate the multi-factorial nature of the pathogenetic process the thought to underlie HIV encephalopathy. Finally, the well characterized GIFN mice will be used to identify and assess in vivo the efficacy of drugs targeted at harmful IFN-CNS interactions. This study provides a unique and powerful approach to elucidate the molecular and cellular basis for the CNS pathobiology of IFN-alpha in vivo and will facilitate the development and testing of therapeutic strategies to alleviate the toxic CNS actions of this cytokine.